<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        // 2、编写一个函数 ，输入一个数字，返还数字的长度
       function num(a){
        var long = String(a);
        return long.length;
       }
       var b = num(3333456);
       console.log(b);
    </script>
</body>
</html>